docs: def stake(self, confidence, value, tournament=1):
          """Participate in the staking competition.
  
          Args:
              confidence (float or str): your confidence (C) value
              value (float or str): amount of NMR you are willing to stake
              tournament (int): ID of the tournament (optional, defaults to 1)
  
          Returns:
              dict: stake information with the following content:
  
                * insertedAt (`datetime`)
                * status (`str`)
                * txHash (`str`)
                * value (`decimal.Decimal`)
                * from (`str`)
  
          Example:
              >>> api = NumerAPI(secret_key="..", public_id="..")
              >>> api.stake(0.1, 10)
              {'stake':
                {'from': None,
                 'insertedAt': None,
                 'status': None,
                 'txHash': '0x76519...2341ca0',
                 'value': '10'}
               }
          """
  
          query = '''
            mutation($code: String
              $confidence: String!
              $password: String
              $round: Int!
              $value: String!
              $tournament: Int!) {
                stake(code: $code
                      confidence: $confidence
                      password: $password
                      round: $round
                      value: $value
                      tournament: $tournament) {
                  insertedAt
                  status
                  txHash
                  value
                  from
                }
          }
          '''
          arguments = {'code': 'somecode',
                       'confidence': str(confidence),
                       'password': "somepassword",
                       'round': self.get_current_round(),
                       'value': str(value),
                       'tournament': tournament}
          result = self.raw_query(query, arguments, authorization=True)
          stake = result['data']
          utils.replace(stake, "value", utils.parse_float_string)
          utils.replace(stake, "insertedAt", utils.parse_datetime_string)
          return stake